Electrical protective device.



No. 820,521. PATBNTED MAY 15, 1905.

0, A. ROLFE. 4 ELECTRICAL PROTECTIVE DEVZ'UE.

AIPPILIIOATIONZFILED JUNE 22. 1903:

UNITED srarns PATENT onion.

CHARLES A. ROLFE, or ADRIAN, MICHIGAN, assrcnoaer MEsr'iitI ASSIGNMENTS,

'TO ROLFE ELECTRIC 00., OF ROGHESTER,:NEYV

Yo K, A CORPORATION or NEW YORK. V ELECTRICAL PROTECTIVE DEVICE,"

. I w i i T (Ml whom It 7mm concern:

Be it known that I, CHARLES A. RoLrE a citizen of the United States,residing at Adrian, in the county of Lenawee and State of Michigan,'haveinvented acertain new and useful Improvement in Electrical ProtectiveDevices, of which the following is a full, clear,

' concise, and exact description, reference be-- ing had to theaccompanying drawings, forming a part of'this specification.

My invention relates to protective devices instrument to .be

Serial No. 154,371, filed April-25, 1903.

for protecting electrical circuits from the injurious effects of'undulystrong currents.

The object of the invention is to provide a simple, inexpensive, andeffective protective In the accompanying drawings, Figure 1 is a view'ofa protective circuit embodying my present invention and also in somemeasure the invention of an'application-filcd by me,

Fig.

2 is a view of the protector proper, and Fig. 3 is a sectiontaken online 3 3 in 2; 1

Referring first to Fig. 1, A is a main circuit,

and a abranch circuits,each containing an being indicated asl, 2, and 3,respectively. 'In accordance with the invention of my said otherapplication I provide a protective dc.-

-vice and connect the same across the terini nals of the instrument, theprotective devices herein shown being indicated as B B B. Each of thesedevices consists of high-resistance material 5, such as gra hits orcarbon, suitably supported by and connected with terminals 6 and 7;mounted on the base {1. The terminals 6 and 7 are connected with thecircuit-wires by suitable cQnnecting-WiresS and 9. A thermometer-tube 10is mounted above the graphite stick 5, with its bulb 11) upon said stickand partially'embedded in a cavity formed therein. The upper end of thetube 10 is connected by wires 12 and 12 with the 'sides of the'circuitwhich the instrument is protecting, and the bulb 11 is connected by aWire 13 with the ground.

The operation of the device is as follows:

Under ordinary conditions and whena normal current is passing throughthe circuit a small portion of it passes through the conductors 8 andHand graphite stick 5; but this portion is insufficient to heat thegraphite Specification of Letters Patent. Application filed June 22,l903- Serial No. 162,597-

operation of a protective I duly strong current, the object being tothus protected, the instruments ed for the purpose Patented May 15,,1906.

' perceptibly. When the current becomes unto the point towhichtlremercury rises when i the temperature is 160 Fahrenheit, this be 'ingthe temperature'at which it is desirable to cause the instrument tooperate.

In my aforesaid other application I have shown generally and described asystem by which the circuit is sh'ort-circnited upon the device by anunshort-circuit the circuit and allow one protector, to be used toprotect an instrument, whereas two formerly have been employed, one oneach side of the line. My presentinvention, .it will be seen, isparticularly adapted for use in connection with and upon'that system.

I have also shown in the. drawings, 1;

and 2 fuses 14 14, arranged in the circuit under'protection outsideofthe protective devices B B, these fuses being desirably insert-,

ofoperating upon the inline of currents, whose very rapidly, theprot-ectrusion upon the strength increasestors B B, as'well known, beingintended more particularly for those unduly strong currents commonlyknown as 1 which rise very slowly, sneak-currents.

It will be understood that the construction and arrangement of theprotective device herein shown can be varied and modified withoutdeparting from the spirit of my invention. Hence I wish to be understoodas considering myself not limited to such spocific arrangement orconstruction.

WhatIclaim- I 1. A device of the class specified, comprising a graphitestick, a tube containing mercury and having its lowerend resting uponIOL') said graphite stick, and circuit connections In-Witness Whereoi Ihereunto subscribe controlled by said mercury. my name this 27th day ofJanuary, A. D. IO

2. A device of the class specified, compris- 1903. ing a graphite stick,a tube'containing mer- I 5 cury and having its lower end resting uponCHARLES- ROLFE said graphite stick, and ground and line con- Witnesses:nections controlled by the mercury in the A. MILLER BELFIELD, tube. 1.0. LEE.

